1. Field of the Invention
The present invention relates to an input and output device which includes a flat input unit mounted on a display unit, and inputs while displaying characters and figures inputted by handwriting into the flat input unit in real time, and a terminal device using this. Particularly, the present invention can be preferably applicable to input and output devices which are equipped with terminal devices such as cell phones, mobile terminals, PDAs (personal digital assistances), game machines, digital cameras, digital video cameras, and personal computers, and can input data with sensation of handwriting, and terminal devices including the input and output devices.
2. Description of the Related Art
As means for inputting data into a computer, keyboards are generally known. However, at present, data to be inputted into computers is not only text data composed of arrangement of the alphabet and numerals assigned to a keyboard, but also data to be inputted in a way like handwriting of characters and figures on a paper with a pen. As means for inputting information while looking at a display screen, a mouse, tablets, and touch panels have already been made practicable. However, among these, a mouse is used by users for input operation from positions apart from the display screen, so that the sensation like drawing characters and figures with a pen cannot be obtained.
On the other hand, in the case of an input and output device having a tablet and a touch panel (hereinafter, called a tablet as a general term of these) overlapped on a flat panel display such as a liquid crystal display (hereinafter, referred to as LCD also), a user can input information only by bringing the tip end of an input pen or his/her fingertip close to the display screen, and the inputted data is displayed on the flat display panel in real time. Therefore, by using such an input and output device, the sensation like handwriting of characters and figures on a paper with a pen is obtained, so that this device is used for supporting users to input data into computers.
FIG. 1 is a sectional view showing a conventional input and output device. As shown in FIG. 1, this conventional input and output device includes an LCD 51, a tablet 52 overlapped on this LCD 51, and a pen 53 for inputting data into this tablet 52. In the LCD 51 a TFT substrate 48 on which, for example, data bus lines, gate bus lines, pixel electrodes and thin film transistors (hereinafter, referred to as TFT) are formed and a color filter substrate 49 on which transparent electrodes made of ITO (indium tin oxide) and color filters are formed are provided in parallel to each other, and between the TFT substrate 48 and the color filter substrate 49, a liquid crystal layer 50 is disposed. For example, the TFT substrate 48 and the color filter 49 are glass substrates with thicknesses of approximately 0.5 mm, and in the tablet 52, a film with transparent electrodes made of ITO or the like is laminated and fixed to a supporting substrate, and the thickness of this supporting substrate is approximately 1 mm.
However, the above-described conventional technique has the following problem. As shown in FIG. 1, it is assumed that the tip end of the pen 53 is made contact with the point A of the tablet 52 for inputting image data by a user. In this case, the tablet 52 detects the contact of the pen 53 and outputs the contact position data to the LCD 51, and based on this position data, the LCD 51 displays at the point B corresponding to the position. At this point, as shown in FIG. 1, the point A and the point B are at a distance corresponding to the total thickness of the tablet 52 and the color filter substrate 49 of the LCD 51 from each other. For example, in the case of this input and output device, the thickness of the tablet 52 is 1 mm, the thickness of the color filter substrate 49 of the LCD 51 is 0.5 mm, so that the point A and the point B are at a 1.5 mm distance in total from each other. Therefore, when a user looks at these points, the image looks deep and the user has a sense of discomfort. Due to this “depth feel,” the input operation of the user loses accuracy, and the operation efficiency significantly lowers and makes the user tired.
In order to solve this problem, the following method has been proposed. For example, Japanese Patent Publication No. H4-114224 discloses a technique for reducing the depth feel by using optical fibers. FIG. 2 is a perspective view showing the conventional input and output device disclosed in Japanese Patent Publication No. H4-114224, and FIG. 3 is a schematic sectional view of the identical. As shown in FIG. 2 and FIG. 3, in this conventional input and output device, an illumination back light 58 is provided, and in front of this back light 58, a flat display 57 is disposed. The flat display 57 is a liquid crystal display, wherein two substrates are disposed in parallel to each other, and between these, a liquid crystal layer (not shown) is disposed. In addition, in front of the flat display 57, a parallax correcting plate 56 formed by bundling optical fibers into a plate shape is provided, and in front of the parallax correcting plate 56, a tablet 55 is provided. The tablet 55 detects a contact position of a pen 54 when the pen 54 comes into contact with it. In FIG. 3, a path 59 of light emitted from the back light 58 is shown.
As shown in FIG. 3, the substrate thickness on the user side of the flat display 57 is defined as d1, and the thickness of the tablet 55 is defined as d2. If no parallax correcting plate 56 is provided, the display position on the flat display 57 viewed from a user is the point C positioned on the liquid crystal layer. Therefore, when the pen 54 is made contact with the tablet 55, there is a distance of (d1+d2) between the contact point E of the pen 54 on the surface of the tablet 55 and the display point C on the flat display 57. On the other hand, when the parallax correcting plate 56 is inserted between the flat display 57 and the tablet 55, light that has been emitted from the back light 58 and transmitted through the display 57 is transmitted along the path 59 in the optical fibers of the parallax correcting plate 56, and is imaged at the point D. Thereby, the distance between the display position (point D) and the input position (point E) becomes d2, whereby the depth feel can be reduced in comparison with the case where no parallax correcting plate 56 is provided.
In addition, for example, Japanese Patent Publication No. H10-283114 discloses a technique for forming an image on the surface of an input and output device by using a micro lens and a light diffusion layer. FIG. 4 is a schematic sectional view showing the conventional input and output device disclosed in Japanese Patent Publication No. H10-283114. As shown in FIG. 4, in this input and output device, an electromagnetic exchange type sensor substrate 63 is provided, and in front of this sensor substrate 63, a back light 64, a liquid crystal display unit 65, a micro lens array sheet 69, and a light diffusion layer 70 are provided in this order. In the liquid crystal display unit 65, a liquid crystal layer 68 is disposed between an upper substrate 66 and a lower substrate 67. In addition, in the micro lens array sheet 69, a number of lenses are formed on the upper substrate 66 side. Furthermore, the light diffusion layer 70 diffuses light converged by the micro lens array sheet 69. The sensor substrate 63 detects the position of the tip end of the pen 71 by means of the electromagnetic exchange method.
When the micro lens array sheet 69 and the light diffusion layer 70 are not provided, light transmitted through the point A of the liquid crystal display unit 65 appears to have exited from the point A. Therefore, even when the user tries to make the tip end of the pen 71 contact with the point A from above, the point A and the tip end of the pen 71 deviate from each other at a distance corresponding to the thickness of the upper substrate 66. On the other hand, by providing the micro lens array sheet 69 and the light diffusion layer 70, light that has exited from the point A is converged to the light diffusion layer 70 by lenses formed on the micro lens array sheet 69, and imaged at the point B on the light diffusion layer 70. Thereby, when a user looks at this, the image appears to be displayed at the point on the light diffusion layer 70, whereby the depth feel due to the thickness of the upper substrate 66 can be reduced.
However, the conventional technique has the following problem. With the technique described in Japanese Patent Publication No. H4-114224 shown in FIG. 2 and FIG. 3, the depth feel due to the thickness d2 of the tablet 55 cannot be corrected even by using the parallax correcting plate 56. In addition, since the parallax correcting plate 56 is manufactured by bundling and binding the optical fibers with a resin, it is difficult to manufacture a large-size parallax correcting plate. Furthermore, the number of optical fibers to be bundled increases in proportion to the area, and therefore, to manufacture a plate with a comparatively large area such as a monitor for a cell phone, a PDA, or a monitor of a personal computer, a large number of fibers must be bundled, and the costs are extremely high.
In addition, the technique described in Japanese Patent Publication No. H10-283114 shown in FIG. 4 employs a method in which an image is formed on the surface of the input and output device by using lenses, so that light must be scattered on the surface of the input and output device by the light diffusion layer 70. However, the light diffusion layer 70 scatters not only the light emitted from the liquid crystal display unit 65 but also externally entering light. Therefore, the contrast of the display unit is significantly lowered, and this lowers the operation efficiency of a user. In addition, since light of the image to be displayed is scattered, for example, when a character is displayed, the character becomes blurred or thicker more than the actual image. This use of the light diffusion layer lowers the display quality.